The present invention relates to torque transmitting apparatus in general, and more particularly to improvements in assemblies which are designed to compensate for fluctuations of torque which is transmitted by an internal combustion engine. Still more particularly, the invention relates to improvements in assemblies of the type wherein a first rotary unit receives torque from the crankshaft of an internal combustion engine, wherein a second rotary unit receives torque for transmission to the input element of a change-speed transmission in a motor vehicle, and wherein the two units are rotatable, within limits, relative to each other against the opposition of a damper.
It is already known to employ in torsion damping assemblies of the above outlined type a damper which comprises one or more energy storing resilient elements acting in the circumferential direction of the two units as well as a friction generating device. Reference may be had, for example, to German Offenlegungsschrift No. 28 26 274 which discloses a friction generating device having means for opposing each and every stage of angular movement of the two units (each such unit comprises a flywheel) relative to each other. The magnitude of the force which is generated by the friction generating device is constant all the way irrespective of the direction in which one of the flywheels turns relative to the other flywheel and irrespective of the extent of angular movement in either direction. Such mode of opposing angular movements of the two flywheels relative to each other is acceptable in motor vehicles where the fluctuations in the direction and/or magnitude of torque which is transmitted by the engine are relatively small. The just described situation normally prevails in a motor vehicle which is equipped with an Otto engine. However, the situation is quite different if the vehicle embodies a diesel engine which often causes pronounced or very pronouhced fluctuations in the magnitude and/or direction of torque which is transmitted between the crankshaft and the change-speed transmission, i.e., between the prime mover and the wheels of the vehicle. In such motor vehicles, the aforedescribed friction generating device cannot adequately damp fluctuations of torque within the entire load range, i.e., the device cannot adequately assist the resilient elements in properly opposing changes in the angular positions of the two flywheels relative to each other.